Specificity and levels of nonhost resistance to nonadapted Blumeria graminis forms in barley

Abstract

Summary The genetic basis of nonhost resistance of barley to nonadapted formae speciales of Blumeria graminis is not known, as there is no barley line that is susceptible to these nonadapted formae speciales, such as the wheat powdery mildew pathogen, Blumeria graminis f.sp. tritici (Bgt). Barley accessions with rudimentary susceptibility to an isolate of the nonadapted Bgt were identified. Those accessions were intercrossed in two cycles and two lines, called SusBgtSC and SusBgtDC, with substantial susceptibility to Bgt at the seedling stage were selected. The quantitative variation among barley accessions and in the progenies after convergent crossing suggests a polygenic basis for this nonhost resistance. Both lines allowed an unusually high level of haustorium formation and colony development by Bgt. The SusBgt lines and their ancestor lines also allowed haustorium formation and conidiation by four out of seven isolates of other nonadapted B. graminis forms. Analysis of the infection process suggested that nonhost resistance factors are specific to the form and developmental stage of B. graminis. Resistances to establishment (first haustorium), colonization (subsequent haustoria) and conidiation are not associated. The lines developed will be of use in elucidating the genetic basis of nonhost resistance to Bgt in barley, and in gene expression and complementation studies on nonhost resistance.

Phytosterols Play a Key Role in Plant Innate Immunity against Bacterial Pathogens by Regulating Nutrient Efflux into the Apoplast

“…For example, hypersensitive response (HR) is a typical resistance phenomenon that is associated with both R-gene and some nonhost resistance. Similar global gene expression profiles (Tao et al, 2003) and other induced responses (Zimmerli et al, 2004;Aghnoum and Niks, 2010;Zellerhoff et al, 2010;Hiruma et al, 2011) have been observed during nonhost resistance against fungal and bacterial pathogens.…”

New broad-spectrum resistance to septoria tritici blotch derived from synthetic hexaploid wheat

“…In the absence of the HR, resistance is achieved by reducing the development of fungal biomass, which may occur by reducing infection rates. Such partial, or ‘horizontal’, resistance has been observed in some cereal rust interactions (Aghnoum and Niks 2010; Marcel et al 2008). One of the best-known ‘slow rusting’ loci is the Lr34/Yr18/Pm38 complex (Singh et al 2007), which confers partial resistance to stripe rust, leaf rust and powdery mildew.…”

Overexpression of phytoglobin in barley alters both compatible and incompatible interactions with the mildew pathogen Blumeria graminis

“…The histological observations showed a general decline in the frequency of pathogen attacks stopped by papilla formation in the epidermal cells of the GPHb1 plants. The reduction was most significant for the interaction with the wheat‐adapted H8 isolate, probably because papilla formation is the main response in barley against nonadapted genotypes (Aghnoum & Niks, ). The reduction in papilla formation did not lead to more established infection sites, but instead to an increase in the percentage of penetrated host cells showing HR as a second line of defence.…”